Boxelder bugs

Quick facts

Boxelder bugs like warm areas and are attracted to buildings with a lot of southern or western exposure.

The best time to control them is in the fall and is most effective by sealing openings and the timely use of insecticides

They normally do not cause property damage but they can potentially stain surfaces.

Once they are indoors, the only practical control is physical removal.

They are not a serious problem every year.

Boxelder bugs (Boisea trivittatus) are a nuisance because they enter homes and other buildings, often in large numbers. You might not notice them during summer, but they can become an issue when they try to move into homes during fall to find a warm place to hide for winter.

Identifying boxelder bugs

Adult boxelder bugs

About 1/2-inch long

Black with orange or red markings, including three stripes on the area right behind the head (prothorax)

Wings lay flat over their bodies, overlapping each other to form an ‘X’

Young boxelder bugs (nymphs)

1/16th-inch long

Bright red when they first hatch, they change to red and black as they get larger

Boxelder bugs are "true bugs" and belong to the same family as stink bugs, cicadas and other insects with piercing and sucking mouthparts. They release a bad odor when crushed.

You can see bugs at all stages of development at any given time during the summer.

Boxelder bugs are not a serious problem every year. They are most abundant during hot, dry summers when followed by warm springs.

Life cycle of boxelder bugs

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In Minnesota, boxelder bugs emerge during spring as the weather starts to warm up.

Adults feed on plants and seeds on the ground during spring and early summer. They begin mating a couple of weeks after they start feeding.

Starting in mid‑July, they move to female seed-bearing boxelder trees where they lay eggs on trunks, branches and leaves. They are rarely found on male boxelder trees.

Boxelder bugs may also feed on maple or ash trees. There is no noticeable feeding injury to these trees.

During years of high populations, you may find nymphs on the ground or in gardens feeding throughout the summer.

They are most abundant during hot, dry summers when followed by warm springs. They were very numerous in 1988, 1987, 1978, 1977, and 1975. They were also abundant in 1958, 1949, and the hot dry years of 1936 and 1935.

Boxelder bugs start to leave the trees where they were feeding to find protected areas for the winter. Adult boxelder bugs can fly several blocks, and may travel as far as two miles.

Although nymphs may be present in the fall, only fully grown adults survive the winter.

Boxelder bugs like warm areas and are attracted to buildings with a large southern or western exposure.

Buildings standing taller than surrounding structures or standing alone on flat ground can also attract large numbers of boxelder bugs. The color of the building doesn't matter.

As the weather cools, boxelder bugs push into cracks and spaces around homes. They are often found inside around windows.

Boxelder bugs are active until it becomes cold.

Some boxelder bugs end up in sheltered areas in walls, attics and other places inside where they stay until it warms up.

During winter, boxelder bugs are generally inactive. However, during mild, sunny days indoors, boxelder bugs become mobile with warmer temperatures.

Individuals only live for a few days up to a week, though you may still see large numbers of them.

As they wake up, the insects follow the warmth into the home's living areas from where they’ve been hiding in walls or attics. Once there, they move towards windows and other sunny areas. However, warmth may not reach all of the insects and they do not all become active at the same time.

By spring, all the surviving boxelder bugs that overwintered inside buildings become active. They try to move outdoors but many remain trapped inside. They do not reproduce in homes. All the boxelder bugs seen inside during winter and spring entered buildings the previous fall.

Keeping boxelder bugs out of your home

The best way to manage boxelder bugs is to keep them from entering your home from the start.

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The best way to manage boxelder bugs is prevention—keep them from entering your home from the start.

Boxelder bugs on hosta plant

This is done by sealing possible entry points around the home so they are unable to enter plus using an insecticide at the right time.

Make repairs to openings they can get into before the end of August.

Repair or replace damaged window and door screens.

Repair or replace damaged screens in roof and soffit vents, and in bathroom and kitchen fans.

For stucco, plaster, stone or brick buildings

Check outside surfaces for spaces and cracks that may allow insects easy entry, sealing any openings 1/8th inch or larger. This will not eliminate all boxelder bugs but it can significantly reduce the number entering buildings.

Check for gaps and cracks where different materials meet such as brick and wood siding.

Seal cracks with caulk such as silicone, elastomeric latex or silicone/acrylic.

For stone or brick veneer the bottom of the walls will have weep holes that must not be sealed up. Get ventilation plugs to put in the weep holes from your local hardware store.

For vinyl sided buildings

Older houses with vinyl siding may have too many gaps to keep out boxelder bugs completely.

Newer houses are often sealed with a house wrap underneath the siding that keeps most insects from entering homes. But they still may nest between the siding and the wrap.

Large numbers usually collect around doors and other entryways during the fall.

Use an insecticide on areas where bugs gather at doors and around windows.

Once boxelder bugs are found inside the best option is to remove them with a vacuum or a broom and dust pan. It is not practical to try to treat wall voids and other hiding places to prevent them from emerging.

Since they don't live for very long, insecticides are not recommended once they have emerged into the inside of a home.

When boxelder bugs are active, they do not live indoors more than a few days.

They do not reproduce inside.

They can stain walls, curtains and other surfaces with their excrement.

They may be found around houseplants looking for water.

When they come out in the spring, spraying insecticide does not prevent more from returning.

Boxelder tree with seed pods

Boxelder trees, as well as maple and ash, are common in yards and public spaces and are potential sources of boxelder bugs. The benefits of having these trees in a landscape outweigh the problem of occasional infestations.

Spraying with insecticides or removing boxelder trees in your yard is not a good way to manage boxelder bugs. Adult boxelder bugs can fly up to a couple miles from their source of food so they don’t need to be near the trees in order to infest your house.

If large numbers of boxelder bugs are present or you have a history of boxelder bug invasions, you can supplement non-chemical control methods with an insecticide treatment around the outside of your home.

The best time to spray is late summer and early fall when boxelder bugs are first clustering around the outside of buildings.

When choosing a product to use look under “Directions For Use” for information that says the product can be used on the exterior or outside of buildings. This information is often in small print.

You can find the common name for an insecticide by looking for “Active Ingredients” on the label. Common names of active ingredients available to the public include:

bifenthrin

cyfluthrin

deltamethrin

lambda cyhalothrin

permethrin

An experienced pest control service has the necessary experience to successfully treat your home and may be the best option for the worst infestations.

During spring, you may see boxelder bugs on the outside of homes. These insects are coming out from where they spent the winter and are moving away from buildings.

It is unnecessary to spray these insects as they are not entering homes. Treating them does not have any impact on the number of boxelder bugs found the following fall.

CAUTION: Mention of a pesticide or use of a pesticide label is for educational purposes only. Always follow the pesticide label directions attached to the pesticide container you are using. Remember, the label is the law.